The article titled “Exploring the origin and conceptual framework of the EQ VAS” by Chuang et al. (2025) offers a detailed investigation into the historical development, design rationale, and current conceptual understanding of the EQ Visual Analogue Scale (EQ VAS), a key component of the EQ-5D health-related quality of life instrument.
The primary objective of this review is to clarify how the EQ VAS originated, what conceptual framework supports its use, and whether its design optimally captures individuals’ self-rated health. The authors conducted a two-stage literature review using a snowball approach: a citation search of relevant published studies and a search of grey literature from the EuroQol Group, which has played a central role in the development of EQ-5D.
The study traces the roots of VAS in psychophysics and psychology, noting that the EQ VAS was initially intended as a valuation tool, specifically a warm-up exercise for rating hypothetical health states. Its design—such as the vertical orientation and the “thermometer” appearance with numerical and hash marks—was not originally tailored to assess self-rated health. Despite this, EQ VAS has proven to be a psychometrically valid tool for self-assessment in both clinical and general populations.
A critical insight from the article is the lack of a systematically developed conceptual framework for the EQ VAS. The tool is widely used as a patient-reported outcome measure (PROM), but ambiguity remains about what respondents are truly assessing when marking their health on the scale. Qualitative studies show variability in how people interpret labels such as “best imaginable health,” with interpretations influenced by physical, mental, social, and even existential dimensions.
Design features of the EQ VAS, particularly the bipolar end-labels and dense hash marks, are also scrutinized. These elements may discourage respondents from using the full scale or introduce interpretation bias, which could undermine the consistency and comparability of the measure. Some participants, for instance, view “best imaginable health” as an unattainable ideal, leading to conservative ratings even when no health problems are reported.
The discussion section draws attention to the broader implications of these findings. While the EQ VAS remains a standardized and widely accepted measure within the EQ-5D suite, its continued use may benefit from reassessment in light of modern expectations around scale clarity and conceptual grounding. The authors suggest that aligning the EQ VAS more closely with theories underpinning single-item self-rated health (SRH) could enhance its interpretive power—especially since SRH is known to be a strong predictor of mortality and morbidity.
In conclusion, the article calls for a nuanced reevaluation of the EQ VAS, urging further research into its design, digital adaptations, and the cognitive processes it engages. Such work is essential if the tool is to maintain relevance and accuracy in diverse populations and modes of administration.
Reference :
Chuang, L.-H., Kind, P., Kohlmann, T., & Feng, Y.-S. (2025). Exploring the origin and conceptual framework of the EQ VAS. Quality of Life Research. https://doi.org/10.1007/s11136-025-03947-6
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